This disclosure pertains to digital telephony over packet networks, such as Voice over Internet Protocol (VoIP) calling.
Outbound VoIP telephone calls may be serviced by session border controllers (SBCs) that allocate resources to handle the voice media data and control signaling associated with each voice call. The SBCs may work in conjunction with a least-cost router (LCR) to determine the most economical means for routing calls to their destinations. For example, a service provider may have a choice between using internal pathways and using call capacity offered by another service provider to terminate call, and each option may have unique associated costs.
Unfortunately, not all calls can be connected, and many calls may be undesirable for other reasons. For example, many of the calls coming in to an SBC may be nuisance calls, such as spam or unwanted political advertisements. Further, such calls may be dialed at random by the caller, and may therefore be more prone to being directed to numbers which are not in service.
It may not be possible to screen such calls using the Internet protocol (IP) source address of each call. For example, the same IP address may be used for many different call originators, and therefore the IP address itself be used for both spam and legitimate telephone traffic.
Undesirable calls received at an SBC place an unnecessary capacity burden on the SBC. For example, for a call placed to a number that is out of service, the inability to terminate the call may be discovered only after media and control resources have been allocated to the call. Once allocated, these resources are then unavailable to service legitimate traffic. An SBC may then have to be inefficiently large, therefore, or multiple SBCs may need to be employed to encompass the extra capacity needed to handle the bad calls.
Some call originators exhibit a variety of problematic calling behavior. For example, if a call cannot be completed on a first SBC, a caller may connect attempt the call through a second SBC, despite the fact that the call had no chance of being completed, e.g., because the recipient's phone number is not in server. In this scenario, SBC resources are doubly wasted, since the waste is repeated on each SBC on which the call is attempted.